1. Field of the Invention
The present invention is related to a Delay-Locked Loop (DLL), or more particularly, a DLL with power-saving function.
2. Description of the Prior Art
Please refer to FIG. 1. FIG. 1 is a diagram illustrating the Dynamic Random Access Memory (DRAM) system 100 of the prior art. The DRAM system 100 comprises the DLL 110 and the DRAM 120. The DRAM system 100, according to the DLL 110, controls the DRAM 120 to access the data. DLL 110 generates a delayed clock signal CLKD by receiving the reference clock signal CLK, delaying the reference clock signal CLK with a fixed phase, and accordingly generating a delayed clock signal CLKD. In other words, the clock signal CLK and delayed clock signal CLKD have the same frequency, but the phase of the delayed clock signal CLKD and the clock signal CLK is statically differentiated by the phase PD. The DRAM 120 comprises input ends I1 and I2. The input end I1 is utilized to receive the delayed clock signal CLKD and the input end I2 is utilized to receive the turn-off signal SCKE. When the DRAM 120 does not receive the turn-off signal SCKE, the DRAM 120 accesses the data according to the delayed clock signal CLKD. When the DRAM 120 receives the turn-off signal SCKE, the DRAM 120 stops receiving the delayed clock signal CLKD and the data accessing is stopped.
When the DRAM 120 receives the turn-off signal SCKE, the DRAM 120 stops receiving the delayed clock signal CLKD and the data accessing is stopped. In the meanwhile the phase of the delayed clock signal CLKD of the DLL 110 and the clock signal CLK does not need to be differentiated by the phase PD precisely. Due to the DLL 110, after rebooting, needs a long time to generate the delayed clock signal CLKD with the fixed phase difference PD compared to the clock signal CLK (indicates the delayed clock signal CLKD is locked to the clock signal CLK) and this wait time is too long and unacceptable for the DRAM 120. Hence, the DLL 110 cannot be turned off completely as the DRAM 120 is turned off after receiving the turn-off signal SCKE. The DLL 110 needs to maintain normal operation while the DRAM 120 is turned off from receiving the turn-off signal SCKE, which consequently causing electrical power waste and diminish the convenience of the DRAM system 110 of the prior art.